Mid-term results of endoscopic mitral valve repair and insights in surgical techniques for isolated posterior prolapse

Contemporary data arises controversies about the “real-world scenario” of MVS with the enthusiasm for the higher repair rates and lower morbidity associated to less-invasive approaches fading when compared to the actual share of sternal-sparing techniques [2]. Evidence of excellent long-term outcome of MIMVr has been emerging for almost a decade [8–11]. Notwithstanding, it is somehow limited to reference centers worldwide [12‐14]. Evidently, detractors’ skepticism regarding the reproducibility of these remarkable long-term results undermined the dissemination of MIMVr. This study provides mid-term outcome of endoscopic MVr performed via a right anterior mini-thoracotomy. Our series demonstrates noteworthy early postoperative results: low 30-days mortality, low incidence of complications and short length of hospital stay, in line with data published in a recent analysis of more than 10,000 patients who underwent MIMVS from the STS ACSD [2]. Furthermore, we report a considerably low stroke rate (0.3%) despite our institutional set up encompasses retrograde perfusion. This is probably determined by the strict arterial line pressure control that is accomplished in all cases. No difference in terms of postoperative stroke rate between conventional sternotomy and less-invasive approaches was also highlighted in retrospective propensity-matched series and well-conducted meta-analyses [15, 16]. Moreover, a recent systematic safety study based on pre-specified 30-days major complications defined by the MVARC reported a 30-days mortality of 1.2% and a stroke rate of 0.3% in a cohort of 745 patients undergoing MIMVS [17]. Hence, our data confirm and even strengthen the available knowledge of early safety and efficacy of MIMVr [8‐10]. Our institutional MIMVr set-up also includes percutaneous right internal jugular vein cannulation, thus a double peripheral venous cannulation is chosen over the single femoral cannula approach. We believe this aspect safeguards from undesirable complications like the iatrogenic damage to the right atrium, possibly caused by mispositioning the single venous cannula while exposing the mitral valve. More to the point of safety, we used to exclude obese patients from our endoscopic program during the learning curve. Conversely, we have no absolute exclusion criteria nowadays. Notwithstanding, pectus excavatum is considered a relative criterion requiring precise evaluation.

Interestingly, we report CPB and cross-clamp times of 126 and 93 min, respectively. A finding consistent with other published series [8‐15]. The mainstream perception of prolonged surgical times associated with MIMVr fosters the idea of minimally invasiveness as a worthlessly painstaking work. However, a multi-center propensity score matched study showed that this “delay” is limited to 5-to-10 min in dedicated centers [3]. It must also be noted that a reduced thrombo-inflammatory activation is associated with MIMVS as compared to traditional sternotomy, despite significantly longer CPB and cross-clamp times [18].

Long-term favorable outcome and repair durability are the cornerstones of MVr. Assessing the reproducibility of the long-term results obtained with sternotomy is therefore mandatory. We recorded clinical and echocardiographic follow-up data that demonstrate a 5-year survival of 97.3%, and a freedom from replacement or residual MR\(\ge\)3+ of 94.5%. The Leipzig group has been providing one of the most considerable series of MIMVr with an outstanding long-term follow up that shows a 5-year survival of 87% (decreasing to 74% at 10 years) in a cohort of more than 2,800 patients [13]. Glauber et al. conducted another remarkable follow-up study of 1,137 patients who had MIMVr via right thoracotomy between 2003 and 2013 [19]. They reported a 5-year survival of 93.5% and a 94.8% freedom from reoperation (dropping to 90.1% and 94.8% at 10 years, respectively). McClure et al. published data from a series of 1,000 patients who underwent MIMVS (923 repairs and 77 replacements) [14]. The Boston group reported a 93% 5-year overall survival, and a 96% freedom from reoperation after MIMVr, respectively reduced to 79% and 90% at 15 years. All the more since excellent results have been provided by several cardiac centers worldwide, adopting different less-invasive approaches (e.g., mini-thoracotomies, partial sternotomies, parasternal approaches) and visualization strategies (e.g., direct-vision, video-assistance, robotic), resorting to different reparative techniques (e.g., resection, neochords, edge-to-edge repair, etc.), to treat different pathologies (i.e., mainly degenerative etiology, Morbus Barlow, secondary MR, endocarditis etc.), for different patients (i.e., different age, risk factors, EuroSCORE or STS score, comorbidities, undergoing isolated MIMVr or combined surgery). Paradoxically, the heterogeneity within the available literature represented itself the test bench for MIMVr.

Furthermore, over a decade of MIMVr operations, we have been experiencing a surgical evolution with the most commonly performed technique, namely the Carpentier-type leaflet resection with or without sliding annuloplasty, nowadays being outnumbered by non-resection repairs at our institution. Indeed, we apply the running suture technique described by Tirone David: we pass the suture through the fibrous portion of the papillary muscle then in the free margin of the prolapsing scallop and then again in the papillary muscle with the same needle and suturing the two ends on the free margin.

Since the early reports [20], the chordal replacement has been shown to exceptionally perform by complying with the triad bedrock of MVr described by Alain Carpentier himself almost 40 years ago: preservation of physiologic leaflets motion, large surface of coaptation, and annular stabilization [21, 22]. Peremptory evidence of satisfactory long-term outcome was provided by Tirone David, who pioneered the ePTFE cordal repair technique. David et al. published the results of a 25-year experience encompassing data from 606 consecutive patients treated with ePTFE chordal replacement, mainly used to treat AML prolapse. Mean clinical follow-up was 10.1 years (maximum 23 years), the Kaplan–Meier estimated survival was 98.1%, 85.7%, and 66.8% respectively at 1, 10, and 18 years, whereas the freedom from reoperation at 1, 10, and 18 years was 98.6%, 94.7%, and 90.2%, respectively [23]. The Leipzig group lately provided data of their 15-year experience with more than 2,000 patients undergoing MIMVr. Of these, 1,751 (82.1%) had isolated loop repair. Interestingly, Pfannmueller et al. reported a significantly higher 10-year survival (both all-cause and cardiac) in the “respect” group as compared with those who underwent resection MIMVr, namely 85.6% and 81.0% [12]. Even more recently, Lang et al. published the long-term outcomes of 346 patients who had annuloplasty and chordal replacement for degenerative MR (73% of these with a less-invasive approach), from 2003 to 2010. Mean follow-up was 10.8 years (maximum 15.8 years) and again revealed excellent long-term outcomes, with a 10-year survival of 83.3% together with a low incidence of reoperation of 7.8% [24]. Despite this top-tier evidence, the analysis of the STS ACSD shows that neochords implantation nowadays accounts for just one-third of degenerative MVr [25]. In this landscape, given our progressive shift towards a “respect” approach, we sought to ascertain the possible differences in terms of long-term results between leaflet resection and neochords implantation in a homogeneous cohort of patients (i.e., isolated PML pathology). Finally, our subgroup time-to-event analysis for overall survival and freedom from MR ≥ 3 + showed no differences between the techniques. Interestingly, even if annuloplasty ring of similar sizes were implanted in the two cohorts, no difference in terms of postoperative mean gradient was observed. Indeed, a recent multicenter randomized controlled trial, gainsaid the hypothesis of functional mitral stenosis following leaflet resection versus preservation [26].

However, MVr is not just dichotomous. The answer to the “resect” or “respect” diatribe was perhaps provided by Tirone David, who published his outstanding long-term MVr results from a series of 746 patients with challenging degenerative MR (i.e., bileaflet pathology) [27]. A 20-year cumulative incidence of reoperation with death as a competing risk of 4.2% was reported. Notably, 75% of patients received a combination of chordal replacement and leaflet resection, a percentage that increased to almost 90% in those with bileaflet prolapse. Hence, when dealing with complex pathology (i.e., multisegment or bileaflet disease) it is crucial to get further acquainted with integrating different MVr strategies, in order to guarantee optimal long-term results.

This study has some limitations. The most important one is its retrospective observational design. Moreover, despite our institutional approach to MIMVr has remained relatively unchanged over the last decade (i.e., the time period of the study), some other modifications within our perioperative management (e.g., anaesthetic technique, perfusion materials, general perioperative care) may perhaps represent a potential “treatment era bias”. Furthermore, a progressive shift towards a “respect” MVr over the years was noted and above discussed. Another noteworthy limitation is pertinent to our echocardiographic follow-up that partially relied on external cardiologists, without any standardized protocol for the execution of the examination and the interpretation of the results. Besides, although strongly recommended, not every patient received yearly follow-up echocardiographic examination.